Conditions for Fano resonance excitation in 2D array metallic particles
Abstract
In this paper, we study the excitation conditions of Fano resonance of gold ellipsoid nanoparticles in an ordered array located in a homogenous medium (air) and on an optical waveguide. By controlling the period of the array, the diffracting surface mode of the 2D array or the waveguide's eigenmode coupled with the incident wave can be tuned around the local plasmon resonances of the individual gold nanoparticles, under which the fundamental criterion for the Fano resonance is fulfilled, namely a spectrally overlap between a broad resonance and a narrow discrete mode. However, we find that in some cases, Fano resonance could not be excited efficiently even the above condition is satisfied. By analyzing the field distribution of the respective resonance modes, we conclude that the in addition to the above requirement of spectral overlap, the two modes with different line-widths must have the same electric field component in order to excite Fano resonance. Our results give a deeper understanding of the physics of Fano resonance, as well as a strategy in the design of nanophotonic structures and devices that are based on Fano resonance.
